# Continuous Integration

## Definition
Continuous Integration (CI) is a DevOps practice where developers frequently merge their code changes into a shared repository, triggering automated builds and tests to detect integration issues early.

## Key Characteristics

### Across DevOps Maturity Levels
| Maturity | CI Practice Level |
|----------|-------------------|
| Phase 1 | None — manual integration, siloed development |
| Phase 2 | Introduction — version control for code and configurations |
| Phase 3 | Automated builds and tests integrated into the development process |
| Phase 4 | CI pipeline with automated quality gates, performance and load testing |
| Phase 5 | Zero-touch CI pipeline with real-time data for decision making |

### Core CI Elements
- Automated builds triggered on every code commit
- Automated unit, integration, and end-to-end tests
- Static code analysis and security scans
- Fast, reliable build pipelines
- Immediate feedback to developers

## Role in DevOps Maturity

CI is a foundational DevOps practice. Organizations cannot advance to higher DevOps maturity without robust CI. At Phase 3+, CI is combined with continuous delivery (CD) to form CI/CD pipelines.

Key progression:
1. **Phase 2**: Version control introduction, superficial automation
2. **Phase 3**: Most builds automated, security scans in the pipeline
3. **Phase 4**: Immutable infrastructure managed through CI pipelines
4. **Phase 5**: Zero human intervention — all code changes pass through automated pipeline

## Metrics
- Build success rate
- Build frequency
- Mean time to build
- Code coverage percentage
- Test pass rate
- Time to first failure detection

## Sources
- [[sources/devops-maturity-model-from-traditional-it-to-advanced-devops.md]]
- [[sources/cloud-devop-maturity-guideline.md]]

## Related Concepts
- [[concepts/CI-CD-Pipeline]]
- [[concepts/Continuous-Deployment]]
- [[concepts/DevOps-Maturity]]
- [[concepts/Infrastructure-as-Code]]
- [[concepts/DevSecOps]]